This study assessed a tea tree oil-based Pickering emulsion (PE) for preserving refrigerated hairtail (Trichiurus haumela). Over a 10-day refrigerated storage period, PE treatment significantly inhibited microbial proliferation compared with an untreated control. Specifically, PE reduced total viable counts by 0.53 log CFU/g and psychrotrophic viable counts by 0.58 log CFU/g at day 10 relative to the control group. These reductions indicate that PE exerted measurable bacteriostatic or bactericidal effects in the stored product under the conditions reported.
In addition to microbiological counts, the study measured conventional freshness indices. Application of PE led to lower levels of chemical spoilage indicators commonly used to evaluate fish quality. On day 10 of storage, PE-treated hairtail showed reductions of over 33% in both total volatile basic nitrogen (TVB-N) and thiobarbituric acid reactive substances (TBARS) compared with control samples. These findings suggest that PE not only slowed microbial growth but also attenuated biochemical processes linked to protein and lipid degradation during chilled storage.
Volatile compounds associated with spoilage were evaluated during storage. Although the PE introduced an initial odor influence attributable to terpenoids from the tea tree oil, it effectively suppressed formation of spoilage volatiles such as trimethylamine and ammonia over the storage period. Suppression of these nitrogenous volatiles aligns with the observed reductions in TVB-N and supports a functional effect of PE on the metabolic pathways or microbial taxa responsible for producing these compounds.
The reported >33% decreases in TVB-N and TBARS at day 10 indicate that PE limited accumulation of volatile basic nitrogen and secondary lipid oxidation products, respectively. The authors present these chemical outcomes as evidence that PE mitigates both microbial-driven and oxidative spoilage processes in refrigerated hairtail.
High-throughput sequencing was used to profile the microbial community during refrigerated storage and to examine how PE treatment influenced community composition and diversity. According to the report, PE maintained microbial diversity relative to control by preferentially inhibiting Pseudomonas spp., which were identified as a core specific spoilage organism in this system.
By targeting or suppressing Pseudomonas, PE altered the trajectory of community succession. The sequencing data indicated changes in relative abundances among spoilage-associated taxa, with consequences for the overall metabolic activity of the community and the production of spoilage-associated volatiles.
Sequencing and correlation analyses revealed interactions between spoilage taxa. The study reports that PE disrupted a cooperative spoilage network between Pseudomonas spp. and Brochothrix spp. In treated samples, inhibition of Pseudomonas appeared to break cooperative dynamics that contribute to spoilage acceleration in the control group.
Correlation analysis further suggested that Brochothrix spp. may possess higher stress tolerance than Pseudomonas spp. when exposed to PE; however, the authors note that this putative difference in stress tolerance requires additional validation. The report does not provide experimental confirmation beyond the sequencing correlation and therefore explicitly frames Brochothrix tolerance as a hypothesis derived from community-level data.
Taken together, the microbiological, chemical, volatile, and sequencing results indicate that a tea tree oil-based Pickering emulsion can modulate microbial community succession and metabolic activity in refrigerated hairtail, with associated reductions in key spoilage indicators. The authors conclude that PE shows potential as a natural preservation strategy to extend the shelf life of aquatic products.
Reported limitations and points requiring further research include the sensory impact of initial terpenoid odor from the tea tree oil and the need to validate the proposed stress-tolerance differences between Brochothrix and Pseudomonas. The summary in the source notes that the suggestion of higher Brochothrix stress tolerance under PE treatment "requires further validation," indicating that mechanistic or targeted microbial experiments were not included in the reported data.
Overall, the study provides integrated evidence—microbial counts, volatile compound analysis, chemical spoilage indices, and high-throughput sequencing—that a tea tree oil-based Pickering emulsion can reduce spoilage activity and alter community dynamics in refrigerated hairtail, supporting its potential use as a natural preservative in aquatic products.